System and method for monitoring, displaying and recording balloon catheter inflation data

ABSTRACT

An electronically controlled syringe system for connection to a balloon catheter or other balloon-type member and for automatically monitoring, displaying and recording inflation data when the syringe system is used to inflate the balloon catheter or other balloon-type member. A syringe having a barrel and a syringe plunger is selectively operable to increase fluid pressure applied to the balloon catheter or other balloon member by sliding the plunger further into the barrel. Positive pressure applied to the balloon catheter or member can be released by withdrawing the syringe plunger toward the rear of the barrel. A piezoresistive semiconductor transducer housed on the barrel of the syringe senses positive fluid pressure applied by the syringe. The electric signal output by the transducer is input to a controller where the signal is digitally processed so as to derive and record therefrom electronic data representing the magnitude or applied fluid pressure, and so as also to derive the length of time that positive fluid pressure is applied and the electronic data representing this information is automatically displayed and recorded. The controller is also programmable to permit optional selection and input of various control parameters, such as a maximum positive inflation pressure that is to be applied, maximum duration for applying positive inflation pressure, initialization of the date and time of an inflation procedure and/or retrieving and displaying inflation data previously recorded for any prior inflation of the balloon catheter or other balloon member.

Appendix A, referred to herein, may be found in the microfiche appendixcontained in the PTO file for this patent document. The microficheappendix is comprised of one microfiche having twenty seven frames.

A portion of the disclosure of this patent document contains material towhich a claim of copyright protection is made. The copyright owner hasno objection to the reproduction by anyone of the patent document or thepatent disclosure as it appears in the Patent and Trademark Officepatent file or records, but reserves all other rights with respect tothe copyrighted work.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to syringe systems that are used for controllingthe inflation of a balloon-tipped catheter, and more particularly to asystem and method which utilize an electronically monitored syringesystem to assist in the control of balloon catheter inflation pressuresand to automatically record balloon catheter inflation data.

2. The Present State of the Art

Balloon-tipped catheter systems have been known and used in the medicalarts for a number of years in connection with a variety of differentkinds of procedures which are used, for example, in various fields ofmedicine, such as urology, gynecology, cardiology and others.Particularly in connection with the treatment of coronary arterydisease, the use of balloon-tipped catheters and their associatedsyringe systems have become widely used.

Coronary artery disease is the narrowing of the arteries that feedoxygen-rich blood to the heart. Since the heart is a muscle whoseprimary job is to pump oxygenated blood throughout the body, the heartneeds adequate amounts of oxygen to properly function. Thus, when thecoronary arteries which are located on the top of the heart and throughwhich oxygenated blood is returned to the heart become narrowed orblocked (a condition known as "stenosis"), angina can result. Angina isa symptom of coronary artery disease characterized by chest pain orpressure that can radiate to the arm or jaw, and is caused by a lack ofoxygen-rich blood to the heart muscle. Coronary artery disease with itsaccompanying symptom of angina results from atherosclerosis, which is abuild up of waxy material called plaque inside the arteries. When thishappens, under exertion or stress, the heart demands more oxygen but thenarrowed coronary arteries cannot supply enough oxygen-rich blood tomeet the demand, resulting in angina.

Up until about ten years ago, there were two basic ways to treatcoronary artery blockages: with medicine or by performing coronaryartery by-pass surgery. Various kinds of medication could beadministered which would decrease the work of the heart by slowing theheart rate, dilating the blood vessels, or lowering blood pressure.However, such medicinal treatment did not cure coronary artery blockage,which thus remained and which would therefore continue to present a riskthat at some point the blockage would become serious enough to requiresurgical intervention.

In coronary artery by-pass surgery, a blood vessel from the chest or legis grafted beyond the point of blockage so that the blood detours pastthe blockage in order to reach the heart In some severe cases, multipleby-passes are performed. As is well known, coronary artery by-passsurgery is expensive, is a high risk procedure and often requiresprolonged hospitalization and recovery periods.

About ten years ago, another method for treating coronary artery diseasewas developed, called balloon coronary angioplasty, or more technically,percutaneous transluminal coronary angioplasty (PTCA). PTCA is a muchless traumatic procedure than coronary artery by-pass surgery. PTCAtakes about two hours and can be done under local anesthesia, with theresult that often a patient can be back on his feet and active in amatter of days. Because PTCA is much less expensive and less traumaticthan by-pass surgery and yet in many cases still effectively removesblockage, PTCA has experienced a dramatic increase in the number of suchprocedures performed each year. For example, according to some reports,as recently as 1987 some 200,000 patients suffering from coronary arterydisease were treated by PTCA. Since coronary artery disease remains thenumber one cause of death, with (as of 1987) some six million reportedcases in the U.S. alone, PTCA may be expected to continue to play animportant role in the treatment of coronary artery disease.

In performing PTCA, an introducer sheath is inserted through an incisionmade in the groin or in the artery of an arm. An x-ray sensitive dye isinjected into the coronary artery through a catheter that is introducedthrough the sheath The dye enables the doctor, through the use of realtime x-ray techniques, to clearly view the arteries on a televisionmonitor and to thereby locate the artery blockage. A balloon-tippedcatheter with a guide wire at the end of it is then advanced through theartery to the point of the blockage with the help of the x-ray monitor.

As schematically illustrated in FIGS. 1A-1C, the balloon catheter 10 isadvanced to the middle of the blockage 12. The catheter 10, which isfilled with a fluid and is coupled at its other end to a controlsyringe, is manipulated by the cardiologist. Once the balloon catheteris in place, utilizing the control syringe the balloon is inflated for20 to 60 seconds as shown in FIG. 2B. The balloon is then deflated andthis procedure is repeated typically several times to compress theplaque on the arterial wall, as shown in FIG. 1C. After the results arechecked, the balloon catheter and guide wire are then removed.

As will be appreciated, notwithstanding that PTCA is a much lesstraumatic procedure than coronary artery by-pass surgery, nonethelessexacting control with respect to inflation pressure and duration of theinflation periods is essential to the safety of the patient. Forexample, when the balloon catheter is completely inflated so as to begincompressing the plaque, blood flow to the heart is thereby temporarilyshut off. This creates the potential for initiating cardiac arrest.Accordingly, the pressure exerted on the artery by the balloon catheteras well as the duration of the blockage created by inflating the ballooncatheter must both be carefully controlled by the attending cardiologistand other personnel. The inflation pressures and duration of eachinflation must be based on the cardiologist's assessment of the healthof the patient and the patient's ability to withstand such a temporarystoppage of blood flow to the heart.

In the past, PTCA syringe systems have utilized syringe systems whichare equipped with standard pressure gauges that are utilized to senseand read the pressure used for purposes of inflating a balloon catheter.Human observation of stop clocks and the like has been used to controlthe duration of the inflation.

While these prior art techniques have been widely used with success,there is still a serious risk of human error when using such systems.The gauges used on such syringe systems are often awkward and difficultto accurately read, and are also subject to malfunction. Thus, improperrecording of inflation pressure and/or duration may occur. Accordingly,there is a need for the cardiologist and/or clinician to be able toimprove the degree of control and precision with respect to theinflation procedure. There is also a need to be able to accuratelyrecord the procedure data so that in the event of any later questionwith respect to whether the procedure was properly carried out, there isan accurate record from which to answer such questions. The system andmethod of the present invention provide an effective solution to theseproblems which have not heretofore been fully appreciated or solved.

SUMMARY OF THE INVENTION

The system and method of the present invention have been developed inresponse to the present state of the art, and in particular, in responseto the problems and needs in the art not heretofore fully or completelysolved by syringe inflation systems used in connection with PTCAprocedures. However, it is not intended that the system and method ofthe present invention will necessarily be limited solely to PTCAprocedures, since they will also find useful application withpotentially many kinds of procedures which require the utilization ofinflatable balloon members for various kinds of medical procedures.Thus, it is an overall object of the present invention to provide asystem and method which provide for more accurate measurement,monitoring and recording of the pressures used for inflation of aballoon-type member as well as the duration of inflation in connectionwith any such inflation of a balloon-type member, catheter or otherwise.

Another important object of the present invention is to provide a systemand method whereby state of the art electronic technology can beutilized to assist the cardiologist or clinician in accuratelymeasuring, monitoring and recording inflation pressures which he or shedesires to achieve when utilizing a syringe system to inflate a ballooncatheter or other balloon-type member, and which will at the same timeautomatically electronically record and store the inflation pressure andduration of the inflation so as to permit the data pertaining to theprocedure to be later printed out and thus accurately documented andsaved for later reference.

Another important object of the present invention is to provide animproved syringe system and electronic monitoring and recording systemwhich increase the convenience and safe utilization of a ballooncatheter or other balloon-type inflation member.

These and other objects and features of the present invention willbecome more fully apparent from the following more detailed descriptiontaken in conjunction with the drawings and claims, or may be learned bythe practice of the invention.

Briefly summarized, the foregoing and other objects are achieved in anelectronically monitored syringe system that is connected to a ballooncatheter or other inflatable balloon-type device through tubing. Thesyringe comprises a barrel and a plunger selectively operable toincrease fluid pressure applied to the balloon catheter through theconnecting tubing by sliding the plunger further into the barrel, and tothen remove the applied pressure by returning the plunger to the rear ofthe barrel. A transducer means for sensing fluid pressure applied by thesyringe is placed in fluid communication with the syringe and theconnecting tubing. The transducer means thereby senses applied fluidpressure and outputs an electrical signal proportional to the sensedpressure. The electrical signal output by the transducer means is thenelectronically processed so as to derive and record therefrom electronicdata representing the magnitude of fluid pressure applied to the ballooncatheter or other balloon-type member, and so as also to derive thelength of time that inflation pressure is applied to the ballooncatheter or other balloon-type member, and the electronic datarepresenting these parameters is then automatically displayed and/orrecorded. The system also comprises a display means for selectivelyoutputting a visual display of the magnitude of the applied pressure andthe corresponding length of time that inflation pressure is applied tothe balloon catheter or other balloon-type member with respect to eachinflation thereof.

The electronic control system used in conjunction with the system andmethod of the present invention may also be optionally designed topermit the selection and input of various control parameters such as amaximum positive inflation pressure that is to be applied, a maximumduration for applying positive inflation pressure, initializing the dateand time of the procedure and/or retrieving and displaying inflationdata previously recorded for any prior inflation of the balloon catheteror other balloon-type member. In this manner, the system and method ofthe present invention provide not only more convenient operation of thesyringe when inflating the balloon catheter or other balloon-typemember, but also a much safer and more accurate procedure which can beused to effectively alert a cardiologist or clinician when theappropriate levels of pressure and duration thereof have been reachedwith respect to a particular inflation event. The system is thusefficient and easy to operate while at the same time providing improvedconvenience and overall safety, and also providing accuratedocumentation of all inflation data for later reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently preferred embodiments and the presently understood bestmode of the invention will be described with additional detail throughuse of the accompanying drawings, wherein corresponding parts aredesignated by the same reference numerals throughout, and in which:

FIGS. 1A-1C are partial cross-sectional views which schematicallyillustrate a conventional balloon catheter being placed within a vesselsuch as a coronary artery containing a blockage, and showing the mannerin which the blockage is essentially removed by inflation of the ballooncatheter.

FIG. 2 is a perspective illustration showing the system of the presentinvention, and in particular illustrating a syringe with tubing forconnection to a balloon catheter, and a transducer means mounted on thesyringe and electrically connected to an electronic controller.

FIG. 3 is a partial cross-sectional view of the syringe barrel that moreparticularly illustrates one presently preferred structure and methodfor placing the transducer means in fluid communication with theinterior of the syringe and the tubing which is connected to the ballooncatheter.

FIG. 4 is a functional block diagram which schematically illustrates theprimary components of one presently preferred electronic circuit used inconnection with the electronic controller.

FIGS. 5A and 5B taken together constitute a detailed electricalschematic diagram which illustrate, as an example, the presentlypreferred embodiment and presently understood best mode for implementingthe electronic circuit means of the system and method of the presentinvention.

FIGS. 6A through 6D taken together illustrate a flow chart showing onepresently preferred method for programming the digital processor of theelectronic circuit means in accordance with the method of the presentinvention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT

The following detailed description is divided into two parts. In partone the overall system is described, including a description of thesyringe system, the transducer means and electronic controller byreference to FIGS. 1 through 5. In part two the method by which thesystem of the present invention is used to electronically monitor,display and automatically record inflation data is described, includinga detailed description of one presently preferred method for programmingthe digital processor used in the electronic controller by reference toFIGS. 6A-6D.

I. THE SYSTEM

A. General Environment and Intended Utility of the System

As noted above, the system and method of the present invention have beendeveloped in response to specific needs which have been found to existin connection with techniques that are currently in use according to thepresent state of the art which has developed in connection with PTCAprocedures. As described in connection with FIGS. 1A-1C, PTCA is asurgical procedure used for treating coronary artery disease wherein aballoon catheter 10 is inserted through an incision made in the groin orin the artery of an arm and is then advanced through the artery by meansof a guide catheter and assisted by means of an x-ray sensitive dye. Theballoon catheter 10 is advanced until it is located at the middle of theblockage 12. Once located at the middle of the blockage 12, the ballooncatheter 10 is then inflated (see FIG. 1B) to a pressure that istypically between 7 and 10 atmospheres for a duration of between 20 to60 seconds. The balloon catheter 10 is then deflated and the procedureis repeated a number of times, slightly increasing the inflationpressure each time so as to further compress and thereby reduce theblockage 12 created by the buildup of plaque along the wall of theartery. Once this series of inflations is completed and the artery iscleared, as shown in FIG. 1C, the balloon catheter 10 is removed.

While the system and method of the present invention are particularlyuseful in connection with the aforementioned PTCA procedure, the systemand method of the invention are not intended to be necessarily limitedto use in connection with PTCA. Rather, it is contemplated that thesystem and method of the invention will find useful application withrespect to any procedure requiring the use of an inflatable balloon-typemember. Moreover, while in PTCA the inflation pressure which is appliedto the balloon catheter 10 is applied hydraulically by means of thesyringe and connecting tubing which are all filled with a sterile liquidsuch as a solution of saline and contrast medium, in some potentialapplications it may be necessary or desirable to apply the inflationpressure pneumatically. Accordingly, as used herein the term "fluidpressure" is intended to apply either to a hydraulically or apneumatically applied inflation pressure.

B. The Presently Preferred Syringe System and Electronic Controller:FIGS. 2-5

The system of the present invention is comprised of a syringe that isconnected to a balloon catheter or other balloon-type member throughtubing. The syringe is used to apply fluid pressure to the ballooncatheter or other balloon-type member through the tubing so as toinflate the balloon catheter or balloon member when desired, and canalso be used to deflate the balloon catheter or balloon member after ithas been inflated for a selected duration. The system is also comprisedof a transducer means for sensing applied fluid pressure and foroutputting an electrical signal proportional to the sensed fluidpressure. The transducer means is thus preferably in fluid communicationwith the syringe and the tubing connected to the balloon catheter orother balloon-type member. The system also comprises an electroniccircuit means connected to the transducer means for receiving theelectrical signal that is output by the transducer means and forprocessing the electrical signal so as to derive and record therefromelectronic data representing inflation pressure applied to the ballooncatheter or balloon member as well as the length of time the inflationpressure is applied to the balloon catheter or balloon member each timeit is inflated. The system is also comprised of display means which iselectrically connected to the electronic circuit means for selectivelyoutputting a visual display of the inflation pressure and thecorresponding length of time the inflation pressure is applied to theballoon catheter or balloon member during each inflation.

In the preferred embodiment illustrated in FIG. 2, the overall system isgenerally designated at 14 and the syringe is generally designated at16. With reference to FIGS. 2 and 3 taken together, the syringe 16 iscomprised of a barrel 22 typically molded from transparent plasticmaterial to permit inspection of the contents thereof. A syringe plunger24 (FIG. 2) is slidably mounted within the barrel and is secured withinthe barrel 22 of means of a cap 34 which can be threadingly or otherwisesecurely attached at the end of the barrel 22. The syringe plunger 24has a threaded portion 30 which mates with corresponding threads 32 (seeFIG. 3) of end cap 34.

The proximal end of plunger 24 is provided with a soft rubber bulb 25which engages the interior of barrel 22 in a fluid-tight fit such thatby sliding the syringe plunger 24 further into the barrel 22, positivepressure exerted on the fluid contained within syringe 16 and connectingtubing 38 will be applied to the balloon catheter which is connected tothe tubing 38 by means of a rotatable luer connector 39. Similarly, bywithdrawing the syringe plunger 24 toward the rear of the barrel 22, thepositive pressure exerted on the balloon catheter will be released.

Rapid movement of the syringe plunger 24 is accommodated by means of atrigger mechanism comprising a spring-activated trigger 28 which can beretracted into handle 29 so as to disengage the threads 30 from thecorresponding threads 32 of cap 34. This permits the plunger 24 tofreely slide in either direction within the syringe barrel 22. Byreleasing the compression on trigger 28 relative to handle 29, thethreads 30 are then permitted to engage the corresponding threads 32 ofcap 34 so that thereafter the syringe plunger 24 can only be advanced orretracted by screwing the plunger 24 either clockwise or counterclockwise, respectively. Thus, rapid application or release of pressureapplied to the balloon catheter can be accomplished by compressing thetrigger 28 against handle 29 followed by movement of the syringe plunger24 to the position desired for the approximate pressure to be applied.This can then be followed by release of the trigger 28 and screwing theplunger 24, which will permit a slow, gradual adjustment of the syringeplunger 24 to the exact pressure that is desired.

It will be appreciated that insofar as providing for application andrelease of positive inflation pressure, this function of syringe 16 ofthe system could be provided by any of a number of syringe systems whichare conventional or known in the art. However, the syringe illustratedand generally described in connection with FIGS. 2 and 3 is presentlypreferred in connection with the system and illustrates the presentlycontemplated best mode of the syringe 16. A more complete description ofsyringe 16 and its unique design and advantages is contained incopending U.S. application Ser. No. 325,561, U.S. Pat. No. 5,057,078filed concurrently herewith, which is incorporated herein by reference.

The transducer means of the system of the present invention is generallydesignated in FIGS. 2 and 3 at reference numeral 18. As shown best inFIG. 3, the body of syringe barrel 22 has a small rectangular housing 40formed at the leading end of the barrel as an integral part of thesyringe barrel 22. The housing 40 communicates through a small circularopening 50 formed in the sidewall of syringe barrel 22 with the interiorof syringe barrel 22 for the purpose of providing fluid communicationfrom the interior of barrel 22 and connecting tubing 38 to thetransducer means, as hereinafter more fully described.

As used herein, the term "fluid communication" is intended to mean thepneumatic or hydraulic transmission (direct or indirect) of fluidpressures exerted within the syringe barrel 22 and connecting tubing 38to the transducer means so that such fluid pressures can be sensed bythe transducer means. Direct transmission of such fluid pressures wouldoccur, for example, when a diaphragm of a piezoresistive semiconductortransducer is placed into contact (either pneumatically orhydraulically, or a combination of both) with a fluid contained in aclosed system, as would be the case in the preferred embodimentillustrated and described herein. Indirect transmission could be said tooccur, for example, where the transducer means is coupled to a diaphragmthat in turn contacts the fluid contained in a closed system.

In FIG. 3, the transducer is shown as preferably comprising apiezoresistive semiconductor integrated circuit 42 which provides aWheatstone bridge, as shown in the detailed electrical schematic at FIG.5B at the corresponding reference numeral. Transducer 42 is in turnattached to a small ceramic substrate 44 which contains additionalcircuitry for providing temperature compensation and calibration of thetransducer 42, and to which is connected the electrical cable 46. Theend of electrical cable 46, ceramic substrate 44 and piezoresistivesemiconductor transducer 42 are assembled as illustrated in FIG. 3 andplaced within housing 40, and then secured by a suitable pottingcompound and permanently enclosed by means of the cap 48 placed on topof the housing 40. In this manner, the entire transducer assembly isformed as an integral attachment to the syringe barrel 22. The smallcircular opening 50 may be filled, for example, with a silicone gelwhich will permit transmission of the fluid pressures exerted by meansof syringe 16 through the circular opening 50 so that such pressures canbe sensed by transducer 42, while at the same time isolating theintegrated circuit 42 and substrate 44 from coming into contact withfluid contained in the syringe barrel 22.

Stops 26 (see FIG. 1) are formed on the syringe plunger 24 so as toprevent the bulb 25 of syringe plunger 24 from being inserted to thepoint where it would otherwise close off the circular opening 50.

While in the preferred embodiment the transducer means has beenillustrated and described as a piezoresistive semiconductor which isintegrally mounted to the syringe barrel 22, it should be appreciatedthat the preferred embodiment is illustrative only and is not to beconstrued as limiting the scope of the invention. For example, thesemiconductor transducer could be located at the end of connectingtubing attached through a T-connector to tubing 38 and could thereforebe located at a position remote from the syringe 16, as for example onan I.V. stand or mounted as part of the electronic circuitry containedinside of controller 20. Furthermore, the transducer means could alsocomprise transducer types other than the piezoresistive semiconductortype illustrated and described in the preferred embodiment, as forexample conventional strain gauge transducers which have been known andused in the art for many kinds of different pressure monitoringapplications, or fiberoptic transducers.

With further reference to FIG. 2, the electrical cable generallydesignated at 54 is comprised of two lengths as shown at 46 and 58. Thefirst length 46 of cable 54 is permanently attached at one end totransducer 18 in the manner described above in connection with FIG. 3.The other end of length 46 terminates in a conventional connector 60which attaches to the second length 58 of cable 54. The second length 58of cable 54 in turn attaches by a conventional connector 62 to theelectronic circuitry contained in controller 20. Advantageously, byproviding a point at connector 60 which is intermediate the transducer18 and controller 20, transducer 18 and syringe 16 can be disconnectedfrom the controller 20 so that the syringe 16 can be conveniently movedto a different location for testing or the like while still maintainingthe sterility of syringe 16 and transducer 18. Thus, while thecontroller 20 may not necessarily be sterile, sterility of the firstlength of cable 46 and the transducer 18 and syringe 16 can bemaintained at all times.

With continued reference to FIG. 2, the electronic circuit means anddisplay means of the system of the present invention are illustrated inthe preferred embodiment as comprising part of controller 20. Thespecific electronic circuitry which is used for purposes of processingthe electrical signals output by transducer 18 through cable 54 iscontained inside of controller 20 and is more particularly illustratedin FIGS. 4 and 5A-5B, as hereinafter more fully described. The displaymeans of the system is shown in the illustrated embodiment ascomprising, in addition to corresponding parts of the electroniccircuitry, a digital readout as generally designated at 66 which is partof the control panel 64.

Specifically, control panel 64 comprises a menu switch 74 which, whenactivated, will cause a series of optionally selectable functions to bedisplayed at the digital readout 66. Select switch 76 of control panel64 can then be used to input various control parameters as well ascausing the controller 20 to retrieve and display previously recordeddata, as hereinafter more fully described. Controller 20 is alsoequipped with a conventional connector 78 for a printer cable 80 so thatdata which is recorded by controller 20 can also be selectively printedout for permanent documentation and later reference.

The digital readout 66 of control panel 64 is shown in the illustratedembodiment as comprising a conventional LED or LCD alphanumeric displayhaving twelve or any other suitable number of controllable displaypositions for outputting numbers or letters. The display 66 ispreferably also divided into a display portion 68 ("NUMBER") whichdisplays and records the number of each discrete inflation of theballoon catheter. A second display portion as illustrated at 70 ("TIME")is used for purposes of checking and/or inputting the current date andtime, as well as inputting control data with respect to a maximumduration for applied positive pressure, as desired, and is also used forpurposes of displaying the duration of the inflation and signalling asystem user if a selected time of duration has been reached. Displayportion 72 ("PRESSURE") is similarly used for purposes of inputtingselected control data with respect to a maximum positive inflationpressure desired in connection with any inflation, and also selection ofthe pressure units (e.g., either atmospheres or pounds per square inch),and is also used to display the current inflation pressure and to signalthe user if a selected maximum inflation pressure has been reached.

Controller 20 can be conveniently located on a stand 82 at a point whichis easily visible by the cardiologist or clinician using the system andcan be switched on or off using a conventional switch located on thecontroller 20. The controller 20 is also plugged into a conventional ACwall outlet from which the power is derived for purposes of running thecontroller 20, and is also provided with a battery-backed memory whichprovides an internal clock and timer, and which retains data after thecontroller 20 is switched off.

With reference next to FIG. 4, the electronic circuit means of thesystem is more particularly illustrated. In the presently preferredembodiment, the electronic circuit means comprises, by way of example,means for amplifying the electrical signal output by the transducermeans; means for converting the amplified signal from an analog to adigital form; digital processor means for processing the digital form ofthe signal so as to derive therefrom digital data from which themagnitude of the applied pressure, the length of time that pressure isapplied to the balloon catheter and whether the applied pressurecorresponds to a first or a subsequent inflation of the balloon cathetermay be output in a numerical form; data memory means for storing thedigital data derived by the digital processor; and program memory meansfor storing machine-readable instructions utilized by the digitalprocessor means to derive, store, retrieve and display digital data andto optionally display a series of functions for selection at the displaymeans of various control parameters.

With particular reference to the presently preferred embodiment of theelectronic circuit means as generally designated at 84 in FIG. 4, thetransducer 42 is electrically connected by means of cable 54 to ananalog circuit 86 which provides amplification and signal conditioning.As more particularly illustrated in FIG. 5B by the portion of thecircuit enclosed by the dashed box 86, the amplifier and signalconditioning circuit 86 is shown in the preferred embodiment as a 100millivolt full scale differential amplifier with an adjustabledifferential gain of forty to one, which is provided by amplifiers U10B,U10D, and U10C.

From circuit 86 the amplified signal is then input as schematicallyrepresented at line 112 in FIG. 4 and as illustrated at terminal H inFIG. 5B to a conventional analog to digital (A/D) converter circuit 88.The A/D converter 88 serves as a means for converting the amplifiedsignal from an analog to a digital form by outputting a series ofcorresponding digital signals which identify the analog signal sensedand input by the transducer 42. As shown in reference to FIG. 5A, in thepresently preferred embodiment the A/D converter 88 is comprised of anintegrated circuit U8. The particular integrated circuit U8 used in theimplementation of the electronic circuit means, as well as theidentification of each of the parts used in the detailed electricalschematic of FIGS. 5A and 5B, is set forth in Table I at the end of thedetailed description. It should be appreciated that the particularcircuit components and circuit design which is illustrated in FIGS. 5Aand 5B are intended merely as an example of the presently preferredembodiment and the presently understood best mode of implementing theoverall functions which are represented by the block diagram of FIG. 4.FIGS. 5A and 5B illustrate in detail the electrical schematic diagramshowing the pin numbers and interconnections for each of the integratedcircuit components and the other circuit elements used in theimplementation of the preferred embodiment. Of course other circuitdesigns can be devised that would also work satisfactorily using eithersoftware driven digital processing circuitry or hardware based circuitdesign.

With continued reference to FIGS. 4 and 5A-5B, the digitized signal isoutput by A/D converter 88 as schematically represented by line 98 andas illustrated in greater detail in FIG. 5A to a digital processor means90. Digital processor means 90 is illustrated in FIG. 5A as integratedcircuit U1. The digital processor is controlled by machine-readableinstructions stored in program memory 94 which are communicated asschematically illustrated in FIG. 4 by means of a data bus 104 runningbetween digital processor 90 and program memory 94. The particularprogram instructions carried out by the digital processor U1 are moreparticularly illustrated and described in reference to the flow chart ofFIGS. 6A-6D, as hereinafter more fully described in part two, and areaddressed by processor Ul through latch circuit 92 and an address busschematically represented at line 108 (FIG. 4).

Briefly summarized, the instructions stored in program memory 94 areutilized by digital processor means 90 to derive from the digitized datathe fluid pressures applied by the syringe 16 to the balloon catheterand to display the sensed pressures at the digital PRESSURE readout 72of control panel 64 (see FIG. 2). The applied fluid pressures are alsoautomatically recorded by digital processor means 90 and stored in thedata memory 96. The output of the digital data to the display 72 istransmitted by way of bus 106 schematically shown in FIG. 4 and thecorresponding electronic circuitry 97 (FIGS. 4 and 5A) which is used todrive the display 72. The processor means 90 can also be programmed todisplay the positive inflation pressure which is output at the LEDdisplay 72 in units of either atmospheres or pounds per square inch asselected by the system user by means of using the menu and selectswitches 74 and 76, as hereinafter more fully explained.

Processor means 90 can also be utilized according to the programmedinstructions contained in memory 94 to monitor and thus assist in thecontrol of the maximum positive inflation pressure to be applied to theballoon catheter by inputting at the PRESSURE readout 72 a maximumpositive pressure using the menu and select switches. This controlparameter is input from the corresponding display circuitry 97 on bus106 and bus 104 to the data memory 96. Thereafter, once the maximumpositive inflation pressure is reached, the digital processor will causethe PRESSURE display 72 to flash thereby signalling the system user thatthe maximum positive inflation pressure has been reached. Thisadvantageously assists the system user in more carefully controlling andidentifying the procedure used with respect to each inflation event.

In a similar manner, a selected duration for which positive inflationpressure is to be applied to the balloon catheter can also be input atTIME display 70 using the menu and select switches. The correspondingdisplay circuitry 95 thus inputs the selected duration time through databuses 106 and 104 to data memory 96. Accordingly, the programmedinstructions contained in memory 94 will thereafter cause the processormeans 90 to begin counting the duration once positive inflation pressurebegins to be applied. The count will be output by processor 90 at theTIME display readout 70 which will flash once the selected duration hasbeen reached, thereby signalling the system user that positive inflationpressure has been applied for the desired length of time. Again, thissignificantly enhances the ability of the overall system to carefullyassist in controlling the inflation procedures according to the selectedparameters.

Data memory 96 is battery-backed so as to retain all data stored thereineven when controller 20 is switched off, and so as to provide aninternal timer for the date and time data and for clocking any selectedmaximum duration times input as described above.

Each of the control parameters which are input at the TIME and PRESSUREdisplays are input and stored as noted above in the data memory 96. Inthis manner, the appropriate control parameters are utilized by theprogram stored in memory 94 and are also automatically recorded in thedata memory 96 for later reference. In a similar manner, once a positiveinflation pressure is applied the processor means 90 will automaticallytime the duration of the positive pressures and this information willlikewise be recorded and stored in the data memory 96 for laterreference, along with a numerical identification input from the NUMBERdisplay 68 which identifies whether the particular inflation event isthe first time the balloon catheter has been inflated or whether theinflation is a subsequent inflation. In this manner, each time theballoon catheter is inflated it is discretely identified and the maximuminflation pressure and time duration data corresponding to thatinflation event are not only displayed but are also automaticallyrecorded and stored in the data memory 96.

A latch circuit 92 is used to control the gating of address data fromdigital processor 90 to the respective memories 94 and 96 and displaycircuits 93, 95 and 97 as is conventional in the art. In the detailedschematic of FIG. 5A, the latch circuit 92 is illustrated at integratedcircuit U2, while the program memory and data memory circuits 94 and 96are shown as the integrated circuits U3 and U4, the particularspecifications of which are identified in Table I. Integrated circuitsfor the number, time and pressure display circuits 93, 95 and 97 arealso shown in FIG. 5A at integrated circuits U5, U6 and U7 with theircorresponding identifications in Table I.

In addition to the digital readout 66 the system of the presentinvention also provides for output of the recorded data from processormeans 90 through serial data lines 100, 102 to a serial data receiverand driver circuit 114, which in turn is connected as schematicallyillustrated at lines 116 to a printer port 78 to which printer cable 80is connected. The serial data receivers and drivers are shown as aconventional integrated circuit identified at U9 in FIG. 5B, and whichis an RS232 driver and serial transmitter.

The supply voltage used for driving the integrated circuits and otheractive circuit elements shown in the detailed schematic diagram of FIGS.5A and 5B is supplied by means of a transformer 120 which is connectedat its output to a full wave bridge rectifier 118. The output ofrectifier 118 is regulated by integrated circuit U11 which is a voltageregulator. The capacitors C5-C13 serve as noise suppression filters foreach of the integrated circuits U1 through U9. With further reference toFIG. 5B, the switch 124 represents the switch on the back of thecontroller 20 which is used to turn the controller on and off and whichconnects the controller through a conventional cord and socket plug 122to an AC outlet.

II. The Method

Attention is next turned to a detailed description of the presentlypreferred method by which the system of the present invention is used tomonitor, display and automatically record inflation data, withparticular reference to FIGS. 6A-6D which illustrate one presentlypreferred embodiment of the instructions which may be utilized tocontrol the processor means 90. As will be appreciated by those ofordinary skill in the art, and as noted above, while the system andmethod as described in reference to the preferred embodiments hereinillustrate the system and method as implemented using state of the artdigital processing design and corresponding program instructions forcontrolling the processor, the system and method could also beimplemented and carried out using a hardware design which accomplishesthe necessary electronic processing, which is thus intended to beembraced within the scope of various of the claims as set forthhereinafter.

With reference to FIG. 6A, when the controller 20 is turned on theprogram starts as indicated at step 126 and then immediately moves tostep 128 which causes the system to initialize. At this step, theappropriate program instructions are loaded into the digital processor.The system then moves to step 130 where it checks to determine whetherthe transducer 42 has been electrically connected by means of the cable54 to the electronic circuitry housed in controller 20. If thetransducer is connected the system then moves as indicated at flag 132to the portion of the programmed instructions illustrated in FIG. 6C. Ifthe transducer 42 has not yet been electrically connected to controller20, the system causes a message to be output on the digital readout 66signifying that the transducer is disconnected (e.g. "NO SYRINGE") andinstructing the system user to press the menu switch 74, as shown atstep 134. The system then moves to step 136 to check whether the menuswitch 74 has been activated and if not returns to step 130 asschematically illustrated at 138 and continues in that loop until themenu switch 74 is activated.

Once the menu switch 74 is activated at step 136, the system then movesto step 140 and causes the readout 66 to display a message inquiringwhether the data previously recorded by the system is to be scrolled(e.g., inflation pressure and duration corresponding to each inflationnumber is retrieved and displayed in sequence) at the digital readout66. If the system user desires to review the previously recorded data,the select switch 76 is activated and the system then implements step144 which causes all of the previously recorded inflation data for eachinflation event to be retrieved in sequence and displayed. If at step140 the system user does not wish to scroll the previously recordedinflation data, the menu switch 74 is again activated which causes thesystem to skip step 144 as schematically illustrated at line 142 so asto proceed with the next inquiry as represented at step 146.

At step 146 the system causes a message to be displayed on the digitalreadout 66 inquiring whether previously recorded inflation data whichhas been stored in the data memory 96 is to be cleared. If select switch76 is activated this causes the processor to clear the previouslyrecorded inflation data from data memory 96, as indicated at step 150.If the previously recorded inflation data is not to be cleared from datamemory 96, the menu switch 74 is activated which causes the system toskip step 150 as illustrated at line 148 and to move to the next inquiryas represented at step 152.

At step 152 the system causes the digital readout 66 to display aninquiry with respect to whether an upper limit is to be set with respectto the maximum positive inflation pressure to be applied with respect tothe next inflation event. If so, the select switch 76 is activated andis used to input the selected maximum positive inflation pressurethrough the data transfer buses 106 and 104 (see FIG. 4), to the datamemory 96 for later reference. If a maximum inflation pressure is notselected at step 52, the menu switch is activated which causes thesystem to skip step 156 and move to the next inquiry as represented atstep 158.

At step 158 the system displays a message at the digital readout 66inquiring whether the maximum duration for application of positivepressure is to be selected. If so, the select switch is again activatedwhich causes the system to move to step 162 and the select switch 76 isthen used to input at the time display 70 the selected duration. Thisselected duration is input by means of the corresponding time displaycircuitry 95 (see FIG. 4) through the data transfer buses 106 and 104 tothe data memory 96 for later reference.

In a manner similar to that described above in connection with thepreceding inquiry steps, the system continues to inquire whether thecurrent time and date are to be displayed, as represented at steps 164and 170, respectively, and if so, by utilizing the select switch 76 asdescribed above, current date and time may be entered at the timedisplay 70. However, the internal clock that is part of the integratedcircuit U4 will typically make it unnecessary to enter these parameters.The system then moves through the series of steps represented at 176,180, 182, and 184 where it determines the pressure units to be displayedat the pressure display 72 as well as determining whether data is to beprinted. After the print inquiry has been responded to by utilization ofthe appropriate menu or select switch 74 or 76 respectively the systemreturns as illustrated at line 138 to step 130.

As will be appreciated from the foregoing, the portion of the programinstructions which are carried out according to the flow chart of FIGS.6A and 6B pertains to that part of the program which permits a series ofoptionally selectable functions to be sequentially displayed forpurposes of inputting various control parameters which are laterutilized in displaying and automatically recording the data, as well asutilizing these control parameters to alert the system user whenselected limits are reached with respect to maximum positive inflationpressure and duration of positive inflation pressures.

Once the transducer 42 has been connected to controller 20 the systemmoves to that portion of the program illustrated in FIGS. 6C and 6Dwhere it then starts as schematically indicated at step 186 by moving tostep 188 so that the electronic circuitry is permitted to stabilize. Atthis step the processor delays all operation of the electronic circuitryfor a selected period of time to permit the circuit components to reacha steady state so that transient conditions will not introduce anyerrors into the data. The system then moves to step 190 where itdetermines the zero pressure of the transducer 42. At this step theprocessor means 90 determines the reading at transducer 42 with nopressure being applied. This zero pressure reading is then stored and issubsequently subtracted or offset against all other pressure readings toassure accuracy of the data.

At step 192 the system again undergoes a check to determine whether thetransducer 42 is still connected to the controller 20. This is a safetyprecaution to make sure that at all times during the inflation procedurethe transducer 42 is electrically connected to the controller 20 so thatthe data is being accurately input, displayed and recorded. If thetransducer is not connected the system first updates the data memory 96(step 193) so as to mark the time of disconnection and then a message isoutput as indicated at step 194 which notifies the system user that thetransducer is disconnected and instructing the system user to press themenu switch 74. If the transducer 42 is still connected the system thenmoves to step 198 and begins to monitor the electrical signal from thetransducer, which signal has been digitized and input to the digitalprocessor as previously described in connection with FIGS. 4 and 5.

The signal from transducer 42 is monitored based on a sample rate thatis a matter of design choice based upon the particular circuit design,which for the illustrated embodiment, is ten times per second. If thepressure which is sensed at transducer 42 is less than one-halfatmosphere, the system moves to that portion of the program whichcommences with step 200. At that step the system first determineswhether it is in the first pass through the loop started by step 200 andif so moves to step 202 where the memory is updated. The effect ofupdating the memory at step 202 is that the time with respect totermination of the last inflation is recorded and stored in the datamemory 96. Once that step has been completed, the system then moves tostep 204. In the alternative, if at step 200 the system determines thatit is not the first pass through this loop of the program, the systemmoves directly to step 204 and displays the current data with respect tothe inflation number, time, and pressure. The system then moves to step206 where the processor checks the menu switch 74.

If the menu switch is activated in this condition the system moves tothe next step 210 where the last inflation data can be marked as aninitial test or not, as desired by the system user. If the initialinflation is merely a test it is marked at step 212 prior to returningto step 192, otherwise the system moves to step 214 to determine whetherany previously recorded inflation data is to be scrolled. If the data isscrolled the system moves to step 216 and retrieves and displays insequence all previously recorded inflation data for each prior inflationevent, otherwise the system jumps to step 218.

Similarly, the system can also proceed through steps 218, 222, and 226which will permit the transducer to again be zeroed (step 220), or toset a new maximum positive inflation pressure (step 224) or to changethe pressure units (step 228) by entering any of these selections usingthe select switch 76.

Once the inflation pressure applied to the balloon catheter begins toexceed one-half atmosphere by insertion of the syringe plunger, thesystem moves from step 198 to the program step 230. At that step thesystem determines whether this is the first time through the part of theprogram loop which beings with step 230 and if so updates the memory atstep 232. The effect of updating the memory at step 232 is that theprocessor causes the duration of the previous inflation to be recorded.After update memory step 232 has been performed, or in each subsequentpass through step 230, the system then moves to step 234 where thesystem checks to determine whether the inflation pressure has reachedany selected maximum positive inflation pressure input for thisinflation event. If the selected maximum inflation pressure is reachedthe system moves to step 238 and causes the pressure display readout 72on control panel 64 to begin flashing so as to signal the system userthat the selected maximum inflation pressure has been reached. If theselected maximum inflation pressure has not been reached or if none wasselected, the system then jumps as illustrated at line 236 to step 240.

At step 240 the system checks to determine whether any selected durationhas yet been clocked with respect to a selected duration for applicationof positive pressure and if so then moves to step 244 so as to cause thetime display readout 70 to begin flashing, thereby signalling the systemuser that the selected duration has been achieved. If no duration isinput or if the selected duration has not been reached the system movesto step 246 as indicated at line 242 which causes the system to displaythe current data with respect to the inflation pressure being appliedand the length of time that positive inflation pressure has beenapplied. The system then returns to the beginning of the loop at step192.

It will be appreciated that the digital processor U1 of FIG. 5A, whichis an 8032 microprocessor as identified in Table I, could be programmedso as to implement the abovedescribed method using any one of a varietyof different programming languages and programming techniques. Attachedhereto as Appendix A is one such program which was prepared for use withthe 8032 microprocessor and the circuit configuration as illustrated inFIGS. 5A and 5B. The attached program comprises a listing of source codeand assembly language for the 8032 microprocessor.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. Accordingly, the describedembodiments are to be considered in all respects only as illustrativeand not restrictive, and the scope of the invention is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

                  TABLE I                                                         ______________________________________                                        Schematic Reference                                                                              Part                                                       ______________________________________                                        X1                 11.059 MHZ                                                 C3                 10Mfd                                                      R1                 8.2K                                                       U1                 8032                                                       U2                 74HC573                                                    C5, C7, C14        .01Mfd                                                     C1, C2             33pf                                                       P1                 CONNECTOR DB25F                                                               AMP 745389-1                                               U4                 DS1243                                                     U5, U6, U7         DL3416 SIEMENS                                             U8                 ADC0834 TI                                                 U9                 MAX233                                                     D1                 IN5291                                                     R4                 30K                                                        U3                 27256                                                      U11                UA7805UC FAIRCHILD                                         C4                 4700 Mfd                                                   PCB 1              Printed circuit board                                      JP3                Female RJ-11 (6 pos-                                                          4 wire)                                                    JP1                HEADER 4                                                   J1                 AC line cord                                               R17                MMSI TRANSDUCER                                            R3                 33K                                                        U10                LM324                                                      R5                 10 K DIP                                                   R7, R9, R10, R11   10K DIP                                                    K6, R8             10K-15T VRN 752-208-                                                          103                                                        R12, R13           100K                                                       R2                 10K                                                        C6, C8, C9, C10, C11, C12, C13                                                                   .01 Mfd                                                    C15, C16           .2 Mfd                                                     T1                 Toltek Custom                                                                 transformer                                                D2                 GI 2KBP04                                                  F1                 .25 AMP                                                    SW1                Micro Switch & Cover                                       ______________________________________                                    

What is claimed is:
 1. A system for monitoring inflation of aballoon-type member and for automatically recording inflation data,comprising:a syringe connected to said member through tubing, saidsyringe comprising a barrel and a plunger selectively operable toinflate said member by applying fluid pressure to said member throughsaid tubing by sliding the plunger within the barrel; transducer meansfor sensing said applied fluid pressure and for outputting an electricalsignal proportional to said sensed fluid pressure, said transducer meansbeing placed in fluid communication with said syringe and the tubingconnected thereto; means for converting said signal output from saidtransducer means into a series of corresponding digital signals; digitalprocessor means for processing said digtial signals so as toelectronically monitor, display and record inflation pressure applied tosaid member and the duration of inflation by performing the stepsof:deriving data from said digital signals which represents a numericalvalue of the magnitude of said applied pressure; deriving data from saiddigital signals which represent a numerical value of the duration ofsaid inflation pressure; electronically storing all said derived datafor later retrieval and output; and automatically displaying saidnumerical values in a visually perceptible manner to a system user oncesaid applied pressure exceeds a selected threshold level; data memorymeans for storing the digital data derived by said digital processormeans for later retrieval and output; program memory means for storingmachine-readable instructions utilized by said digital processor meansto carry out said programmed steps; and display means, electricallyconnected to said digital processor means, for outputting a visualdisplay of the magnitude of said applied fluid pressure and thecorresponding length of time said pressure is applied to said member. 2.A system as defined in claim 1 wherein said transducer means comprises apiezoresistive semiconductor transducer.
 3. A system as defined in claim2 wherein said transducer is mounted to said syringe so as to form anintegral part thereof.
 4. A system as defined in claim 3 furthercomprising an electrical cable attached at one end thereof to saidtransducer and comprising at the other end thereof a connector forattachment to said digital processor means.
 5. A system as defined inclaim 4 wherein said cable comprises a first length permanently attachedto said transducer mounted on said syringe, and a second length of cabledetachably connected to the first length, such that after said cable isconnected to said digital processor means, said syringe and first lengthof cable may be disconnected from said second length of cable at a pointalong said cable that is intermediate said syringe and said digitalprocessor means.
 6. A system as defined in claim 1 wherein said displaymeans is included within a controller.
 7. A system as defined in claim 6wherein said converting means, said digital processor means, said datamemory means, and said program memory means are all included within saidcontroller.
 8. A system as claimed in claim 7 wherein said controllercomprises a control panel and wherein said display means comprises adigital readout on said panel.
 9. A system as defined in claim 8 whereinsaid display means further comprises means for outputting said digitaldata to a printer.
 10. A system as defined in claim 9 wherein saidcontrol panel comprises:first switch means for selecting a menu displayfor presentation at said digital readout at least one of the followingoptionally selectable functions to be performed by said digitalprocessor means: a. retrieving and reviewing all previously storeddigital data; b. clearing all digital data previously stored in saiddata memory means; c. setting a maximum positive inflation pressurevalue; d. setting a maximum inflation time value; e. initializing dateand time; f. selecting units of inflation pressure; g. printing datastored in said data memory means; and second switch means for enteringto said digital processor means data identifying choices selected withrespect to any of said functions.
 11. A system for generating a seriesof discrete balloon catheter inflations and for automatically displayingand recording inflation data corresponding to each said discreteinflation, comprising:a control syringe connected to a balloon of saidballoon catheter through tubing, said syringe comprising a barrel and aplunger selectively operable to first apply and then remove positivefluid pressures to said balloon through said tubing by sliding theplunger within the barrel; a piezoresistive semiconductor transducerconnected in fluid communication with said fluid pressures applied tosaid balloon such that said transducer senses fluid pressures applied tosaid balloon and generates an electrical signal proportional to thesensed fluid pressure; and a controller electrically connected to saidtransducer, said controller comprising:means for amplifying said signaloutput by said transducer; means for converting said amplified signalfrom an analog to a digital form; digital processor means for processingsaid digital form of said signal so as to electronically monitor,display and record inflation pressure applied to said balloon and theduration of inflation by performing the steps of:deriving data from saiddigital signals which represents a numerical value of the magnitude ofsaid applied pressure; deriving data from said digital signals whichrepresent a numerical value of the duration of said inflation pressure;electronically storing all said derived data for later retrieval andoutput; and automatically displaying said numerical values in a visuallyperceptible manner to a system user once said applied pressure exceeds aselected threshold level; data memory means for storing the digital dataderived by said digital processor means for later retrieval and output;and program memory means for storing machine-readable instructionsutilized by said digital processor means to derive, store, retrieve anddisplay said digital data and to optionally display a series offunctions for selection at said display means; and display means forvisually identifying a numerical value for each discrete inflationtogether with corresponding numerical values of said inflation pressuresand duration thereof.
 12. A system as defined in claim 11 wherein saidtransducer is mounted on said barrel so as to form an integral partthereof.
 13. A system as defined in claim 11 wherein said display meanscomprises a digital readout and means for outputting said digital datato a printer.
 14. A system as defined in claim 13 wherein saidcontroller further comprises:first switch means for selecting a menudisplay for presentation at said digital readout at least one of thefollowing optionally selectable functions to be performed by saiddigital processor means: a. retrieving and reviewing all previouslystored digital data; b. clearing all digital data previously stored insaid data memory means; c. setting a maximum positive inflation pressurevalue; d. setting a maximum inflation time value; e. initializing dateand time; f. selecting units of inflation pressure; g. printing datastored in said data memory means; and second switch means for enteringto said digital processor means data identifying choices selected withrespect to any of said functions.
 15. In a system for generating aseries of discrete balloon catheter inflations and for automaticallyrecording inflation data derived from an electrical signal correspondingto each said discrete inflation, an improved control syringecomprising:a barrel connected through tubing to a balloon of saidballoon catheter; a plunger slidably mounted within said barrel andoperable to selectively apply and then release fluid pressure on saidballoon by movement of the plunger within said barrel; a piezoresistivesemiconductor transducer mounted on said syringe barrel and in fluidcommunication with the interior of said syringe barrel through a holeformed in a side of said syringe barrel such that changes in fluidpressure applied to said balloon by sliding said plunger are sensed bysaid transducer, which in turn generates an electrical signalproportional to the sensed positive fluid pressure; and means forpreventing said syringe plunger from occluding said hole.
 16. In asystem comprising an inflatable balloon member connected through tubingto a syringe barrel and wherein a plunger slidably mounted within saidbarrel is moveable to selectively apply and then release fluid pressuresexerted on said balloon member so as to selectively inflate said balloonmember one or more times, a method of monitoring, displaying andautomatically recording inflation data comprising the stepsof:selectively increasing fluid pressure applied to the balloon memberby pushing said plunger into said syringe barrel; sensing the fluidpressure applied by said syringe and outputting an electrical signalproportional to the sensed fluid pressure; automatically electronicallydigitally processing the output electrical signal once a selectedthreshold level of the applied fluid pressure is reached so as toautomatically derive and automatically record therefrom electronicdigital data representing the magnitude of the applied fluid pressuresand the length of time said fluid pressures are applied to the balloonmember; electronically outputting a visual display of the magnitude andthe corresponding length of time that said fluid pressures are appliedto the balloon member; and releasing the fluid pressure applied to theballoon member by pulling said plunger toward the rear of the syringebarrel.
 17. A method as defined in claim 16 further comprising the stepof repeating each of said steps in connection with a second inflation ofthe balloon member.
 18. A method as defined in claim 16 furthercomprising the steps of:electronically selecting and storing a maximummagnitude of positive fluid pressure to be applied to said balloonmember; and electronically outputting an indication to a system userthat signals when said maximum fluid pressure is applied to said balloonmember.
 19. A method as defined in claim 16 further comprising the stepsof:electronically selecting and storing a maximum duration for whichsaid fluid pressures are to be applied to said balloon member; andelectronically outputting an indication to a system user that signalswhen said maximum duration has been reached.
 20. In a system comprisinga balloon catheter connected through tubing to a syringe barrel andwherein by movement of a plunger through the barrel fluid pressureapplied to the balloon catheter may be selectively increased ordecreased, a method of electronically monitoring, displaying andrecording the applied fluid pressure each time the balloon catheter isinflated, the method comprising the steps of:inflating a balloon of theballoon catheter a first time by pushing the plunger into the syringebarrel so as to apply a positive inflation pressure to the balloon;sensing any applied fluid pressure using a piezoresistive semiconductortransducer placed in fluid communication with the applied pressure, andgenerating at said transducer an electrical signal proportional inmagnitude and duration to said applied pressure; converting saidelectrical signal to a series of corresponding digital signals andinputting said digital signals to a digital processor; processing thedigital signals using said digital processor to carry out a programmedmethod comprising the steps of:deriving data from said digital signalswhich represents a numerical value of the magnitude of said appliedpressure; deriving data from said digital signals once the appliedpressure reaches a selected threshold level, said data representing anumerical value of the duration of said positive inflation pressure;electrically storing all said derived data for later retrieval andoutput; automatically displaying said numerical values in a visuallyperceptible manner to a system user once said applied pressure exceeds aselected threshold level; deflating the balloon by withdrawing thesyringe plunger so as to remove the positive fluid pressure applied tothe balloon; and repeating each of the above-recited steps for a secondinflation of the balloon.
 21. A method as defined in claim 20 whereinsaid digital processor is housed within a controller which comprises acontrol panel having a digital readout, and wherein prior to saidinflating step said digital processor performs the step of presenting avisual display at said digital readout of at least one of the followingoptionally selectable functions:a. retrieving and reviewing allpreviously stored digital data; b. clearing all digital data previouslystored in said data memory means; c. setting a maximum positiveinflation pressure value; d. setting a maximum inflation time value; e.initializing data and time; f. selecting units of inflation pressure; g.printing data stored in said data memory means.
 22. A method as definedin claim 20 wherein prior to said inflating step said digital processorperforms the steps of:electronically sensing whether said transducer iselectrically connected to said digital processor; and when sensing thatsaid transducer is not so connected, said digital processor outputtingto a system user a signal to that effect.
 23. A method as defined inclaim 20 wherein prior to said inflating step said digital processorperforms the steps of:presenting an optionally selectable input fordetermining a maximum positive inflation pressure; and electronicallystoring digital data corresponding to said maximum positive inflationpressure in response to a user-determined input.
 24. A method as definedin claim 23 wherein said method carried out by said digital processorfurther comprises the step of presenting to a system user an indicationof when said selected maximum positive inflation pressure is applied tosaid balloon.
 25. A method as defined in claims 20 or 23 wherein priorto said inflating step said digital processor performs the stepsof:presenting an optionally selectable input for a maximum durationduring which positive inflation pressure is to be applied to saidballoon; and electronically storing digital data corresponding to saidselected maximum duration in response to a user-determined input.
 26. Amethod as defined in claim 25 wherein said method carried out by saiddigital processor further comprises the step of presenting to a systemuser an indication of when said selected duration is reached.